[0001] This invention relates to footwear-making equipment, and more particularly, to a
device for stretching uppers over a last preparatory to gluing the edge of the uppers
to a supporting insole which has been secured under the last.
[0002] Known are machines performing various operations for fitting the toe portion of a
shoe over a last. A machine of this kind is described, along with an assembly method,
in Italian Patent No. 912328, for example.
[0003] The basic steps involved in the process consists of placing the uppers onto a last
under which a supporting insole has been secured, clamping the edges of the uppers
in a multiplicity of grippers mounted all around the last, stretching the uppers over
the last by a relative movement of the grippers and the last, locking the uppers to
the last by means of a crescent-shaped member adapted to apply a pressure to the last
edge, gradually releasing the grippers from the uppers, tucking the uppers edge under
the last by means of two movable shaped plates, and adhering the uppers edge to the
insole using a glue which has been coated over the two parts to be joined.
[0004] For the assembly process to be carried out correctly, the grippers should be arranged
around the last such that their clamping points, specifically the sections which border
the respective clamping points, are aligned to one another a predetermined distance
away from the last to follow the contour of the latter, and such that their pull is
applied evenly all around the edge of the uppers. Thus, for each gripper, adjusters
are usually provided which enable a gripper to be moved toward and away from the last,
sideways toward and away from adjacent grippers, and rotated about its axis to evenly
merge with one another the clamping points of adjacent grippers.
[0005] These adjustments are fairly critical and must be performed by qualified personnel,
are time-comsuming, and adversely affect the production rate, and must be repeated
on the occurrence of any change in the shoe design, which is disadvantageous especially
where small volume productions are involved.
[0006] To reduce such adjusting operations, it has been proposed of mounting the grippers
in two sets, each set to a plate pivoted in the proximities of the toe end of the
last, so that the distance of each set from the respective side of the last can be
controlled. However, this expedient has proved only partly successful because, while
enabling the gripper positions to be adjusted within limits so as to accommodate the
width of a footwear article being assembled, it disallows full adaptation of the gripper
clamping pattern to the last.
[0007] It is the object of this invention to provide a device for stretching uppers over
a last, which enables adjustment of the gripper positions in a ready and accurate
manner for automatically adapting the clamping points thereof to the contour of a
footwear article being assembled while keeping the eveness of the clamping pattern
unaltered.
[0008] This object is achieved by a device as generally defined and characterized in the
first of the claims appended to this description.
[0009] The invention can be more clearly understood from the following detailed description
of an exemplary and in no way limitative embodiment thereof, to be read in conjunction
with the accompanying drawings, in which:
Figure 1 is a side view showing schematically a gripper of a device according to the
invention;
Figure 2 is a view of the gripper shown in Figure 1, taken in the direction of arrow
F;
Figures 3 and 4 are plan views showing schematically the most distinctive parts of
a device according to the invention at two different stages of its operation; and
Figure 5 shows in perspective the supporting members for a gripper and the associated
displacement means.
[0010] In Figures 1, 2 and 5, a gripper, generally designated 10, is shown with its supporting
and driving members. In particular, the gripper has a box-type body 11 which is attached
by two arms 13 to a rod 12 into a four-bar linkage. An electric motor 14 is mounted
to the body 11 for oscillation about a pivot pin 15 and is coupled to the four-bar
linkage by conventional means (not shown) for the purpose to shift the gripper 10
along a substantially parallel direction to the longitudinal axis of the rod 12, upwards
as viewed in the drawing. The gripper has two jaws 16 connected to the body 11 for
pivotal movement relatively to each other, and an air-operated cylinder 17 attached
to the body 11. The cylinder 17 is coupled to the gripper jaws by conventional means
for the purpose, of which only one tie rod 19 is partly shown in the drawing figure,
to operate the gripper by opening or closing its jaws 16.
[0011] The rod 12 has an element 12a attached rigidly thereto which is constructed and functions
as a chain link and is mounted to a linkage element or connecting rod 20 for pivotal
movement about its longitudinal axis a-a within a cylindrical socket 21 (Figures 3
and 4) of the connecting rod 20. The latter has two lugs 20a laid opposite each other
into a yoke configuration and being passed through by respective coaxial bores 22
through which a pin 23 extends.
[0012] Shown schematically in Figures 3 and 4 is a supporting and driving structure for
a multiplicity of grippers 10. For convenience of illustration in these Figures, the
grippers, nine in number, are only represented by their incomplete outlines. Shown
in the Figures are the connecting rods 20 and chain links 12a, the latter being connected
pivotally together by pins 24. One of the grippers, the central or apical one shown
at 10a, is made narrower than the others, carries no linkage element 20, and has its
rod fastened rigidly to the bed by suitable means, not shown.
[0013] The structure comprises a rigid supporting part 25 in the form of a cylinder, with
a portion of its surface removed and is fastened to the machine bed. In Figures 3
and 4, this cylindrical part 25 is represented by just two wall portions. It should
be understood, however, that the two portions are joined together at the top of the
Figure and extended into the bottom part thereof to leave a passage for accessing
the center of the structure where the last is accommodated on which the uppers would
be stretched. The last and respective supporting and driving means have not been shown
because conventional.
[0014] The structure further comprises two thick supporting and guiding plates, shown at
26, which are also fastened rigidly to the machine bed by suitable means, not shown,
and extend into the cylindrical part 25 in a common plane perpendicular to the cylinder
axis, with a spacing therebetween. These plates 26 have notches 27 being open to the
machine center and extending radially outwards. Through the thickness of the plates
26 there are provided bores 29 which extend from the bottoms of the notches 27 to
the outward edges of the plates.
[0015] Each notch 27 provides a runway for a slide 28 connected pivotally to one of the
connecting rods 20 by a respective pin 23, only shown in Figure 1. Each slide 28 has
a longitudinal threaded bore 28a (Figure 1) into which an oppositely threaded shaft
30 engages correspondingly in helical fit relationship. The latter extends into the
bore 29 between its respective slide 28 and a bearing coupling 31 mounted on the cylindrical
part 25. The shafts 30 are each driven rotatively by a motor 33 secured on the cylindrical
part 25.
[0016] For adjusting the gripper positions relative to the last, the motors 33 are operated
in a co-ordinate fashion until the various grippers have been moved into a selected
clamping pattern.
[0017] Conveniently, this setting would be performed by an electronic control unit, known
per se, so programmed as to enable a series of adjustments for moving the grippers
into the best clamping pattern for a given footwear article design to be assembled.
In this case, as skilled persons in the art of automatic setting systems will readily
recognize, the position of each gripper must be known each time. For this purpose,
position sensors may be employed which can be coupled either to the slides 28 or the
setting motors 33 and supply each time acknowledge signals of the positions of the
individual grippers to the electronic control unit, or step motors may be used whose
angular settings would be known at all times.
[0018] As may be appreciated, the device of this invention enables optimum setting of the
grippers for any design, shape, and size of a footwear article to be assembled. With
the embodiment providing for an electronic program unit, the various patterns stored
in the unit can be retrieved and changed as required, thereby the gripper positioning
can be adjusted to fit any shapes, sizes, or sides (right or left) of footwear articles
to be assembled, quite rapidly and accurately on all occasions, thus significantly
expanding the machine versatility and production over prior art machines.
[0019] While only one embodiment of this invention has been described and illustrated hereinabove,
it is understood that several variants and modifications are feasible within the scope
of the same inventive concept.
1. A device for stretching uppers over a last on a footwear-making machine, comprising:
a multiplicity of grippers (10) mounted on respective holders (12,20) around the
last for clamping the uppers edges;
drive means (14,17) for the grippers (10);
means (28,30,33) for adjusting the gripper (10) positions relative to the last;
and
means for effecting a relative movement of the last and the grippers along a stretching
direction of the uppers over the last;
characterized in that the holders (12,20) of adjacent grippers (10) are connected
pivotally together.
2. A device according to Claim 1, characterized in that the holders (12,20) for the grippers
(10) comprise each a rod (12) and means (13) for pivotally connecting a respective
one of the grippers (10) to the rod (12), that the rods (12) of the holders lie substantially
parallel to one another, and that the holders (12,20) for the grippers (10) comprise,
for connecting them pivotally together, each a chain link (12a) fast with its respective
rod (12) and means (24) of pivotal connection between that link (12a) and the chain
link (12a) of an adjacent holder.
3. A device according to Claim 2, characterized in that the rods (12) of at least some
of the holders (12,20) for the grippers (10) are mounted for free rotation about their
longitudinal axes (a-a).
4. A device according to Claim 3, characterized the means for adjusting the grippers
(10) in position comprise means (28,30,33) operative to shift at least some of the
holders (12,20) for the grippers (10) along a transverse direction to the pivot axes
of the chain links (12a).
5. A device according to Claim 4, characterized in that the means (28,30,33) for shifting
the gripper (10) holders (12,20) comprise, for each gripper (10), a motor (33), a
first helical coupling member (30) adapted to be rotated by the motor (33), a second
helical coupling member (28) associated with the first helical coupling member, and
a pivotal connection member (20) between that second helical coupling member (28)
and the holder (12,20) of a respective gripper.
6. A device according to Claim 5, characterized in that the second helical coupling member
is a slide (28) movable along a runway (27), and the pivotal connection member is
a connecting rod (20) journalled, with one end, on the slide (28) and with the other
end on the gripper (10) rod (12).
7. A device according to any of the preceding claims, characterized in that the position
adjusting means comprise position sensors for the grippers (10) and an electronic
program unit operative to adjust the gripper positions in accordance with a predetermined
programmed clamping pattern.